This invention relates to gas burners, and more particularly to an improved burner for achieving uniform heating of a cooking surface.
Gas burners are known in the art and have been used in various appliances for heating purposes. For example, a gas burner may be used in a griddle to heat a cooking surface of the griddle, or in a grill which has a rack that supports food at a desired distance above the burner. There are two types of gas burners commonly used in such cooking appliances. The first type is an atmospheric burner that relies solely on the static pressure of the gas from a gas supply to provide an air-gas mixture at various burner outlets where the air-gas mixture may be ignited to create a flame. The second type is a powered burner that utilizes a fan or blower, connected to the supply of gas prior to the inlet to a burner, to enhance air and gas mixing and to further provide the air-gas mixture to the burner at a pressure which is generally higher than atmospheric pressure. Powered burners are especially advantageous when the burner is disposed in an environment which does not lend itself to ready mixing of air with the combustible gas, such as a griddle or grill in an enclosure such as a cabinet.
Powered burners are also capable of providing all of the air needed for combustion directly to the air-gas mixture exiting the burner outlets. In contrast, the combustion gas exiting an atmospheric burner generally requires more oxygen for combustion than is provided at the outlet so the flames flicker and wander more than the flames of a powered burner. Furthermore, because the powered burners have sufficient air for combustion directly at the outlets, powered burners may be placed closer to a surface to be heated without starving the flames of oxygen.
Prior art gas burners exhibit performance deficiencies due to both local and global nonuniform flame characteristics. Local nonuniformities refer to differences at a single burner outlet while global nonuniformities refer to differences among a plurality of burner outlets. These non-uniform flame characteristics of prior art gas burners often create non-uniform heating conditions on a cooking surface. These non-uniform heating conditions manifest themselves as localized hot or cold spots along the cooking surface resulting in unpredictable and inconsistent cooking. Local nonuniform flame characteristics are primarily due to burner geometry. In this regard, prior art burners have generally been constructed from tubing of round or circular cross-sectional shape and have slots or holes formed along the outer surfaces of these tubes. Because the tubes are circular in cross-section, the outlets necessarily extend around the circumference of the tubes whereby the flames emanate from the burner outlets at varying distances from the cooking surface.
Global nonuniform flame characteristics are primarily due to the varying, and generally directional bias of the incoming combustible gas flow. The non-uniform gas flow at the burner inlet results in a non-uniform distribution of gas throughout the gas distribution section. This uneven gas distribution then leads to non-uniform flame characteristics along the gas distribution section.
There is thus a need for a gas burner which may be used with cooking appliances to heat a cooking surface and which overcomes drawbacks of the prior art, such as those described above.
The present invention discloses an improved gas burner which provides a uniform flame front of short, stable flames issuing from outlets of the burner (local uniformity) and which exhibits uniform gas pressure along the entire length of the burner (global uniformity). In an exemplary embodiment, the burner is a powered burner having a fan coupled to an inlet of the burner to mix air with a combustible gas and provide it to the burner at an increased pressure. The burner includes a gas distribution section which is formed from one or more tubular members that have been arranged to form a closed loop. In another aspect of the invention, the tubular members have a rectangular cross-sectional shape. The burner also includes an inlet to the gas distribution section provided at an end of the burner that is coupled to a supply of combustible gas.
The outlets of the burner comprise several slots formed into a substantially flat upper surface of the gas distribution section and arranged to balance the thermal characteristics of the burner. In one embodiment, the outlets are arranged in a spaced parallel fashion along the axial lengths of the gas distribution section such that the slots are oriented substantially transverse to the axial direction of the tubular members. Advantageously, the slots provided on the substantially flat surface of the gas distribution section result in locally uniform flame fronts issuing from the outlets of the burner.
The burner also includes a gas diffuser near the inlet to the gas distribution section. Advantageously, the gas diffuser helps to even the gas flow along the length of the gas distribution section such that the flames issuing from the outlets of the burner are globally uniform in height from the surface of the burner.
In another exemplary embodiment, a cooking appliance includes a cooking surface and a powered burner disposed beneath the cooking surface. The burner has a fan coupled to an inlet of the burner to mix air with a combustible gas and provide it to the burner at an increased pressure. The burner includes a gas distribution section made up of one or more tubular members arranged to form a closed loop. An inlet to the gas distribution section is provided at one end of the burner and is further coupled to a supply of combustible gas. The outlets of the burner comprise several slots formed into a substantially flat upper surface of the gas distribution section. The outlets are arranged in a spaced parallel fashion along the axial lengths of the gas distribution section such that the slots are oriented substantially transverse to the axial direction of the tubular members. The burner also includes a gas diffuser near the inlet to the gas distribution section. The aforementioned burner provides a locally uniform and globally uniform flame front that in turn provides uniform heating conditions to the cooking surface of the cooking appliance.
The features and objectives of the present invention will become more readily apparent from the following Detailed Description taken in conjunction with the accompanying drawings.